Single crystal detectors such as NaI:Tl and many other inorganic salts have been developed and used for gamma ray detection. These single crystals have several the desirable characteristics, including well-defined preparations, light emission at wavelengths suitable for photomultiplier tube (PMT) detection and amplification, efficient light transmission, and uniform light generation and transmission to produce spectra with good full-energy peak resolution. However, they are plagued by several substantial weaknesses that make them difficult or inapplicable to use in non-ideal conditions, e.g. in the field or in a port. These weaknesses include instability due to humidity, mechanical shock, and temperature fluctuations among other issues. Moreover, while materials such as NaI:Tl are excellent for gamma ray detection, they are often inapplicable for detection other forms of nuclear radiation. As an alternative, solid-state detectors far exceed the resolution of these inorganic crystals but so far are limited in size or require operation at very low temperature.
Use of nanoparticles to prepare large detectors for gamma-ray spectroscopy has been proposed to bypass these difficulties. Nanoparticles held in a small matrix have been reported within the past 9 years to yield single peaks attributed to interaction with gamma rays and alpha particles. Sheng Dai et al. prepared CdSe/ZnS quantum dots (1-20 nm dia.) embedded in a thin disk of a clear sol-gel. When the disk was exposed to the 5,300-keV alpha particles emitted by 210Po and the emitted light (peaking at a wavelength of about 590 nm) was collected with a PMT, they observed an energy continuum with a multichannel analyzer. Letant and Wang impregnated a porous glass slab (˜1×1×0.025 cm) with CdSe/ZnS quantum dots, exposed this material to the 59.5-keV gamma rays and 5,500 keV alpha particles emitted by 241Am, collected the emitted light with a PMT, and observed a peak associated with each type of radiation. McKigney et al. attached small pieces of LaF3.Ce particles (<10 nm dia.) embedded in an organic matrix (several mm on a side) to a small Teflon container, exposed them to gamma rays of 59.5 keV and 122 keV emitted by 241Am and 57Co, respectively, collected the emitted light (330 nm) with a PMT, and observed peaks for both radionuclides.
Recently, fabrication methods and optical properties of transparent oxyhalide glass composites containing GdF3 compounds doped with Tb3+, Eu3+ and Dy3+ were studied by Shan et. al. Lakshminarayana et al. further reported on the characteristics of a similar GdF3 glass composite with Pr3+, Sm3+ doping. However, few studies have been conducted in terms of gamma-ray spectroscopy applications. Such materials, utilized in a scintillator, could efficiently convert nuclear radiation to photons of a wavelength detectable by photomultiplier tubes (PMT) while the highly transparent nature of the matrix could potentially give rise to promising efficiency and resolution for nuclear radiation detection.